1. Field of the Invention
The present invention relates to storage control apparatus providing storage resources to upper order apparatus such as a host computer or server etc., and particularly relates to storage control apparatus where a number of storage devices are arrayed so that storage regions are configured using RAID. More specifically, the present invention relates to storage control apparatus supplying to a host a first logical volume that itself does not correlate to a real storage region correlating a second logical volume equipped with a real storage region from the storage resources with the first logical volume, and converting host accesses to the first volume to accesses to the real storage region via the second logical volume. Still more specifically, the present invention relates to storage control apparatus capable of increasing the real storage region correlating with the second logical volume according to accesses from upper order apparatus.
2. Background Art
Storage systems equipped with storage control apparatus, and upper order apparatus such as a server or host computer etc. connecting with this storage control apparatus via a communication path such as a network etc. are well known. Here, upper order apparatus store data on storage devices by logically defining logical volumes that are capable of being accessed by the upper order apparatus and correlating physical storage regions of the storage devices with the logical volumes. It is then possible for the storage control apparatus to read out data stored in the storage device. Hereinafter, the term host may be used to refer to any upper order apparatus. That is, the terms upper order apparatus and host may be used interchangeably.
In recent years, the volumes of data handled by upper order apparatus have dramatically increased, meaning that substantial increases in storage capacity (volume size) of logical volumes is also necessary. It is therefore ensured that upper order apparatus do not run out of storage capacity by ensuring that storage regions allocated to logical volumes are sufficiently large.
However, in the event that a large logical volume is allocated to upper order apparatus while in reality large volumes of data are not handled by the upper order apparatus, regions that are not used periodically cannot be released for use by other upper order apparatus, which is wasteful with regards to storage resources.
Here, allocating storage regions of a storage device to a region of a logical volume where writing is performed when a processor of an upper order computer writes to a logical volume of storage apparatus is proposed (Japanese Patent Laid-open Publication No. 2005-11316). As a result, storage regions can be made active in an effective manner compared to allocating a large volume of storage regions to the logical volume in advance. Further, it is also disclosed in U.S. Pat. No. 6,823,442 that storage control apparatus is provided at a logical volume accessed by upper order apparatus, with physical storage regions then being allocated to this virtual volume.
“Data life cycle management” also exists as a further way of making storage resources of a storage system active in an effective manner. This takes note of the fact that the value of data changes with the passage of time, with data where the frequency of access from upper order apparatus is low or the time that has elapsed from an access is long being moved from online storage to near line storage or back-up devices so that storage regions of comparatively high-value online storage capable of high-speed responses to accesses from upper order apparatus are then made active in an effective manner.
As an example of the related art pertaining to the present invention, there is disclosed in Japanese Patent Laid-open Publication No. 2005-128771 that relates to a data file system etc. provided with a data access server that has physical storage for storing data, receives access requests, and accesses this physical storage, and a data file server that sends access requests to this data access server, utilizes the data access server in data saving, and files data, with physical blocks then being effectively released when logical blocks are not in use.
Further, in Japanese Patent Laid-open Publication No. 2004-127301, a storage control system is disclosed that comprises a mapping system with a virtual storage space and physical storage space that correlates a plurality of addresses of the virtual storage space to each address of the physical storage space, and a controller configured so as to automatically delete parts of the mapping system in accordance with a provision assigning order of priority designating portions to be deleted of the mapping system in accordance with the priority order. Further, storage control apparatus is also disclosed in Japanese Patent Laid-open Publication No. 2006-106980 as an example of related art pertaining to the present invention.